std::is_implicit_lifetime

Defined in header `<type_traits>`
template< class T > struct is_implicit_lifetime;		(since C++23)

std::is_implicit_lifetime is a UnaryTypeTrait.

If T is an implicit-lifetime type, provides the member constant value equal to true. For any other type, value is false.

The behavior is undefined if T is an incomplete type other than an array type or (possibly cv-qualified) void.

If the program adds specializations for std::is_implicit_lifetime or std::is_implicit_lifetime_v, the behavior is undefined.

Template parameters

a type to check

Helper variable template

template< class T >
constexpr bool is_implicit_lifetime_v = is_implicit_lifetime<T>::value;

(since C++23)

Inherited from std::integral_constant

Member constants

value

[static]

true if T is an implicit-lifetime type, false otherwise
(public static member constant)

Member functions

operator bool	converts the object to bool, returns `value` (public member function)
operator() (C++14)	returns `value` (public member function)

Member types

Type	Definition
`value_type`	bool
`type`	std::integral_constant<bool,value>

Notes

Feature-test macro	Value	Std	Feature
`__cpp_lib_is_implicit_lifetime`	`202302L`	(C++23)	`std::is_implicit_lifetime`

Example

// The following types are collectively called implicit-lifetime types:
// * scalar types:
//     * arithmetic types
//     * enumeration types
//     * pointer types
//     * pointer-to-member types
//     * std::nullptr_t
// * implicit-lifetime class types
//     * is an aggregate whose destructor is not user-provided
//     * has at least one trivial eligible constructor and a trivial,
//       non-deleted destructor
// * array types
// * cv-qualified versions of these types.
#include <type_traits>

static_assert(std::is_implicit_lifetime_v<int>); // arithmetic type is a scalar type
static_assert(std::is_implicit_lifetime_v<const int>); // cv-qualified a scalar type

enum E { e };
static_assert(std::is_implicit_lifetime_v<E>); // enumeration type is a scalar type
static_assert(std::is_implicit_lifetime_v<int*>); // pointer type is a scalar type
static_assert(std::is_implicit_lifetime_v<std::nullptr_t>); // scalar type

struct S { int x, y; };
// S is an implicit-lifetime class: an aggregate without user-provided destructor
static_assert(std::is_implicit_lifetime_v<S>);

static_assert(std::is_implicit_lifetime_v<int S::*>); // pointer-to-member

struct X
{
    X(){}
    ~X() = delete;
};
// X is not implicit-lifetime class due to deleted destructor
static_assert(!std::is_implicit_lifetime_v<X>);

static_assert(std::is_implicit_lifetime_v<int[8]>); // array type
static_assert(std::is_implicit_lifetime_v<volatile int[8]>); // cv-qualified array type

int main() {}

is_scalar (C++11)	checks if a type is a scalar type (class template)
is_array (C++11)	checks if a type is an array type (class template)
is_aggregate (C++17)	checks if a type is an aggregate type (class template)
start_lifetime_asstart_lifetime_as_array (C++23)	implicitly creates objects in given storage with the object representation reused (function template)
is_implicit_lifetime_type (C++26)	checks if reflected type is an implicit-lifetime type (function)